Aerospace and military applications often provide unique challenges to design and manufacturing. Often manufacturing requires the assembly of multiple elements within regions providing limited clearance and reduced accessibility. Traditional attachment methodologies and fasteners may be difficult to position within such regions. In addition, assembly of such structures commonly requires precise tensioning of such fasteners to minimize stresses and insure proper functioning. The use of traditional fasteners, such as commonly used bolt assemblies, can result in difficult installation, ergonomic issues, inconsistent torque application, and sub-optimum joint fatigue performance.
One such assembly that suffers from the aforementioned concerns is the wing side-of-body joint assembly used in aerospace applications. The wing side-of-body joint is configured around chordwise stiffeners, typically referred to as chords, used to transmit wing skin and stringer loads into the body and wing center structure. Presently, the fasteners used in this application are high strength protruding head bolts and nuts. The limited clearance present in the chord elements, however, dictates undesirable constraints on how the bolts may be orientated and their installation sequence. Often, limited clearance may make traditional bolt assemblies virtually impossible to utilize or re-torque after installation.
It is also highly desirable to torque bolts from the nut side. Such nut-side torque application is known to deliver consistent optimum joint fatigue performance. Torque application from the head side often results in the bolt turning inside the hole, which can score the bolt and/or fastener and result in galling and improper bolt tensioning. Therefore, it is highly desirable for the fastener assemblies utilized in the wing side-of-body joint assembly to be torqued from the nut side. The limited clearance imposed by the chord elements, however, makes such nut-side torque application unfeasible in certain locations.
What is needed is a method and fastener assembly that is suited for assembly within reduced clearance regions of the joint assembly. Additionally, it would be highly desirable to have a method and fastener assembly that would allow for nut-side only torque application even within such reduced clearance regions.
Further difficulties arise where a fastener assembly requires a precisely tightened nut (threaded head fastener). In wing-side of body joints with low clearance regions, nuts may require tightening to a precise orientation. With prior solutions, this had been done as follows: One end of a bolt is inserted into a low clearance region, and a nut is inserted into the low clearance region. The nut is tightened to some arbitrary degree onto the bolt and then examined to see whether the orientation meets what is required. If the nut is not in the proper orientation, then the nut must be adjusted again. This process must be repeated until proper orientation is achieved. As the nut is located in a low clearance region, examination of the nut is difficult or impossible while it is being tightened. This tightening and re-tightening process requires much trial and error which is time-consuming and difficult. Therefore there exists a need for a fastener which can quickly, easily, and accurately be tightened to a specific orientation.